Head and neck squamous cell carcinoma (HNSCC) is an aggressive malignancy, which afflicts more than 300,000 people worldwide and about 42,000 in the US annually and is associated with severe morbidity and <50% long-term survival. Strategies for prevention of HNSCC include identification of individuals at a high risk to develop such cancers (e.g., individuals with oral premalignant lesions) and to treat them with agents that can suppress the development of additional premalignant lesions and inhibit the development of oral cancer. Early events in the multistep oral carcinogenesis include activation of signaling or metabolic pathways that endow the cells with favorable growth and survival characteristics. Therefore, agents that can inhibit or reverse these changes by targeting molecularly defined pathways are potential novel candidates for cancer prevention and therapy. This project is based on the hypothesis that the arachidonic acid metabolizing enzyme cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR), which are both upregulated in oral premalignant lesions, are important for oral carcinogenesis and are excellent targets for intervention. Therefore, the long term objective of this project is the assess the potential of combinations of the COX-2 inhibitor Celecoxib and the irreversible EGFR inhibitor EKB-569 to act additively or synergistically to suppress prostaglandin production and inhibit EGFR signaling and thereby inhibit the growth or enhance apoptosis in premalignant oral keratinocytes and HNSCCs using in vitro and in vivo models. Normal oral keratinocytes and short- and long-term cultures of epithelial cells derived from dysplastic oral lesions will serve as an in vitro model to study mechanisms of oral carcinogenesis and assess the potential of the above agents. The specific aims are: 1) Analyze surgical specimens from patients enrolled in Project 1 at baseline and after treatment with celecoxib, EKB-569 or their combination for constitutive and treatment-modulated levels of the molecular targets of the agents and consequences of such modulation including changes in the COX-2 product prostaglandin E2 (PGE2) levels, cell proliferation marker and apoptosis; 2) To elucidate the mechanism by which PGE2 induces the proliferation of oral epithelial cells; 3) To establish short-term and long-term cultures of oral dysplastic cells in vitro and characterize the cells and to examine the response of the dysplastic cells as well as normal and premalignant oral keratinocytes and HNSCC cells to celecoxib, EKB-569 and their combinations; 4) To determine whether a therapeutic regimen combining celecoxib and EKB-569 is more effective at inhibiting the growth of HNSCC xenografts than either agent given alone.